(a) Field of the Invention
The present invention relates to a method and apparatus for transmitting and receiving system information in a dual connectivity mobile communication system in which both a master base station and a secondary base station are connected to a mobile terminal.
(b) Description of the Related Art
In 3rd generation partnership project long term evolution/system architecture evolution (3GPP LTE/SAE), the standardization of a small cell enhancement (SCE) technology is in progress. A small cell improvement technology is a technology for densely disposing small cells in a macro cell-based cellular network in a multi-layered manner and increasing the capacity of a wireless network through close coordination between a macro cell base station and a small cell base station. An object of the small cell improvement technology is to accommodate explosive traffic increase and to secure coverage essential for mobile communication and efficient mobility management by densely disposing high-density small cells in order to increase spectrum efficiency per area. In order to achieve the object, a 3GPP radio access network (RAN) has had discussions on a scenario and requirements for small cell improvement in an evolved-UMTS terrestrial radio access (E-UTRA) and evolved-UMTS terrestrial radio access network (E-UTRAN), and has approved a physical layer and high layer study item (SI) for small cell improvement in an RAN conference in December of 2012.
For such small cell improvement in a cellular network taken into consideration in the 3GPP, three scenarios associated with the deployment, spectrum, and traffic of a small cell and compatibility with previous standards have been defined. Further, technical issues and solutions for the defined scenarios have been discussed. In scenario 1, a macro cell and a small cell use the same frequency in an architecture in which the macro cell and the small cell overlap with each other. In scenario 2, a macro cell and a small cell use different frequencies in an architecture in which the macro cell and the small cell overlap with each other. In scenario 3, only a disposed small cell is used in an architecture in which a macro cell and the small cell do not overlap with each other.
In 3GPP, several element technologies for improving performance of a mobile communication network according to the introduction of high-density small cells have been reviewed through the study item period based on such scenarios. As a result of the review, dual connectivity has been suggested as a representative element technology for Rel-12 small cell improvement. Dual connectivity is a technology in which a piece of UE is provided with service using radio resources provided by two or more different network access points connected through non-ideal backhaul.